The most spectacular, the most practical, the most relaxed and nonchalant. They have expression, modesty, sex appeal, simplicity - all I hope for in my clothes. So said the late, great Yves Saint Laurent, a fashion designer famous enough to warrant two biopics this year. What garment seemingly impossibly perfect, idealised even, was Saint Laurent talking about? The humble blue jean.
He isn't alone. For spring/summer 2014, a raft of designers have turned back to the traditional blue jean for inspiration, some cutting it raw and ragged, others twisting, patching, embroidering and bedazzling the fabric until its surface - and its price tag - resemble the costliest of couture silk.
Marc Jacobs appliqued it with Victorian jet and showed jeans under gossamer evening gowns for his swansong show for Louis Vuitton. Junya Watanabe showed distressed skirts as well as the patchwork styles he made a sell-out success for last winter. And Marios Schwab and Marques Almeida leaped into the fray and showed slashed and torn styles in London (a cliche, but the capital is the home of punk). "The frayed denim - it's almost like our logo," says Paulo Almeida, one half of the latter. "We've always got a denim jacket, but it's got a hint of the season," says Marta Marques.
The duality of approach, the co-existence of the raw and the rarefied, is important. "We're interested in the idea of contrasts and something a little more refined, a little more street; and that's the dialogue that we've always been interested in," says Lazaro Hernandez who, alongside Jack McCollough, designs the New York-based Proenza Schouler label.
"Girls ask us all the time, 'What do I wear this jacket with?' And if we say jeans, they say 'Do you guys make jeans?' and we're like, 'no, you'll have to get them from Levi's or something'. So why don't we make our own jeans?"
That was the thought process that motivated the 2012 launch of Proenza Schouler's denim collection. It followed a 2011 collaboration with denim specialists J Brand, who have also worked with designers including Erdem, Meadham Kirchhoff and Christopher Kane (a collaboration with Simone Rocha is on the cards for this year).
Despite the fabric's French origins - the word "denim" is a contraction of serge de Nimes, after the French town where it was originally manufactured - denim has always been a low-cost, work-wear fabric. Serge de Nimes was crafted into jeans or rather, Genes, named after the Genoese sailors who first wore the loose trousers. They could be worn wet or dry, and were easily hauled up when swabbing the decks.
Fashion's elevation of denim, and the jean, from street to chic was relatively recent. First, jeans got cool, courtesy of James Dean and Marlon Brando in the 50s - and cinematic idols are wont to be emulated the world over. Marilyn Monroe donned jeans for her role in River of No Return in 1954, forging an iconic image of female sexuality that sent women flocking to buy Levi's as casualwear.
Despite their ubiquity in pop culture, it wasn't until Calvin Klein in the 70s that any designer thought to stamp a designer name on denim. Klein tweaked the cut to give his jeans a sexiness synonymous with his brand, inspired by the hedonistic clubbers of his favourite haunt, New York nightclub Studio 54. In 1978, Klein's jeans or, simply, Calvins, as they later became known via a provocative ad starring Brooke Shields, sold 200,000 pairs in the first week.
Klein, of course, made millions, as did legions of designer imitators. By the 80s, every label from Armani to Versace had its own line of denim. Even avant-garde labels got in on the act: Vivienne Westwood created denims to sit alongside her main collection, printed with giant polka dots or baroque cherubs. Denim became synonymous with Jean Paul Gaultier, who launched a line cleverly titled Jeans Paul Gaultier to capitalise on the appeal.
When Gaultier launched the haute couture division of his fashion label, Gaultier Paris, in January 1997, denim was a key part. "A long denim coat, all denim coat with black jet," says Gaultier of the first denim look he showed. "Then with feather ... already three or four outfits of denim in my first couture, which is a lot for denim out of 50 outfits!" A selection of those denim looks is on display as part of his forthcoming retrospective at London's Barbican.
Gaultier's haute couture Lesage-embroidered serge de Nimes is an extreme example of a penchant for deluxe denim, but others are getting in on the act. Donatella Versace's spring show was inspired by the girl on the street, and offered cut-out and embroidered skinny jeans, and Olivier Rousteing's Balmain collections have featured high-octane denim from his first season.
This season, a more casual streetwear mood was underlined by the fabric being cut into roomy bomber jackets, slouchy sweatshirts and salopettes (fashion talk for dungarees). By contrast, the idea of anodyne designer denim - of banging your label on a bland pair of blue jeans to make a billion - is over.
That market's done. It's not innovative, concurs Lydia King, buying manager for women's contemporary at Selfridges. She would know: in June last year, Selfridges London store opened a 2400sq m Denim Studio, devoted to every conceivable 21st-century incarnation of the stuff.
Its inventory of more than 11,000 denim items, from £11 ($21) to £11,000, included specially designed pieces by JW Anderson and Givenchy by Riccardo Tisci. Speaking of her customers, King states, "When it's a designer denim piece, they're going for something special but I think that's driven by the designers. I don't think designers, when they're experimenting with denim, want to do something boring and functional."
Yet, at the same time, there's an eternal, universal approachability to denim that appeals to designers and consumers.
"It's more a mood and an attitude," says King. "It really appeals for that non-effort fashion look - Emanuelle Alt [the editor-in-chief of Vogue Paris] just wearing her jeans with a blazer."
"We think it's time for us to do something more democratic," reasons Lazaro Hernandez. And hard-wearing, work-wearing denim is nothing if not democratic.